A. Field of the Invention
The present invention relates to the field of refrigeration and air conditioning. In particular, the present invention relates to the use of ternary refrigerants in refrigeration air conditioning, or heat pump applications and methods of charging and recharging such systems' refrigerants, particularly after some refrigerant has leaked.
B. Description of the Prior Art
Chlorofluorocarbon refrigerants present a threat to the earth's ozone layer. Accordingly, practitioners in the air conditioning and refrigeration art have long sought refrigerant compositions which are as effective as these commonly used chlorofluorocarbon refrigerants, but which are also safe for use in the environment.
Monochlorodifluoromethane, R-22, is one such chlorofluorocarbon refrigerant. (An R-number designation is applied to all commonly used refrigerants by the American Society of Heating, Refrigeration and Air Conditioning Engineers ("ASHRAE"). The R-numbers used herein correspond to the ASHRAE designations, which are widely used by practitioners). This refrigerant unfortunately has some detrimental characteristics, particularly environmental ones.
Practitioners have long searched for an environmentally friendly substitute for R-22. One such practical substitute known in the art is R-407C. R-407C is a ternary refrigerant comprising difluoromethane ("R-32"), pentafluorethane ("R-125") and 1,1,1,2-tetrafluoroethane ("R-1 34a") combined in a mass ratio of 23/25/52, respectively.
While the use of R-407C has environmental benefits over R-22, its use poses certain challenges in practice. One challenge faced by practitioners is that when the composition of the refrigerant changes, for example due to a leak in the refrigeration system, the R-407C composition is difficult to reconstitute. For example, in the case of a vapor leak from an idle system, the respective refrigerants may be lost to different degrees, because each of the three refrigerants has different characteristics. The practitioner normally will not know the extent of the leak and the precise amounts of the respective refrigerants that have evaporated. It therefore will be difficult for a practitioner to know what relative amounts of R-32, R-125, and R134a to add in order to reconstitute the R-32/R-125/R-134a mass ratio. Because these components are present in different relative amounts, the practitioner must add differing amounts of each component separately, based on either a guess, or some type of calculation based on known or sensed parameters. To make matters worse, R-32 is flammable, rendering its presence alone as an independent additive for reconstituting R-407C a safety hazard.